Ingredients:

• 8 dried shiitake mushrooms
• 1 pound pork loin or tenderloin
• 1 tablespoon cornstarch
• 1 1/2 teaspoons sugar
• 1 tablespoon sesame oil
• 1 1/2 teaspoons Shaoxing rice wine, optional
• 4 teaspoons soy sauce
• 1/2 medium head napa cabbage, thinly sliced (about 6 cups)
• 3 medium carrots, julienned
• 1/2 teaspoon kosher salt
• 3 scallions, thinly sliced on a bias
• 2 teaspoons ginger, minced
• 4 cups canola or vegetable oil, divided
• 3 tablespoons oyster sauce
• 1 large egg
• 50 to 60 (6-inch) square spring roll wrappers
• Chinkiang vinegar or black vinegar, to serve